What's going on here then?

Things move on and I have just about completed the bike now and it is ready for its 'first service' after a self-imposed running-in period of 600 miles. Part of that was to join in an Airhead run out (bottom picture) which was from Popham Airfield on 9 Apr 22. This was the first longer-range sortie covering Salisbury to Popham then all over the place to Wantage where I peeled off to take the excellent A338 back home. She went like a dream!

The badges went back on the tank. I put the missing exhaust clamp on.

I found the issue with the horn - the new wiring loom does not match the wiring diagram properly (??) and I had wired in ignition-switched live (green/black) and horn-switched power (brown/yellow) to both sides of the horn . It was easier to fix a short cable to the end of the green/black (from the horn) to the earth terminals in the headlamp than do anything else. Horn works fine.

I took a leaf from Byron's book and experimented with home zinc plating for the seat lock mechanism. Very pleased with the results so now the seat sits down properly. The rear footrests are next.

This photo was taken outside the Green Dragon in Alderbury last night . I rode home in the dark and isn't it nice to have a decent headlamp and all the gauges illuminated?

What a fantastic job. Seeing it being used, parked outside the pub is a great conclusion to the rebuild.

I've just read through the whole thread, a great story and a really lovely motorbike. Very well done.

The bike looks great Tim and a real credit to you and it has even got the correct rear tool box foam cover in place. Not many guys can say that. As you have found out zinc plating is very straight forward and produces great results. I must say I am missing not having the 3 airheads in my garage especially the 80 g/s pd. In fact I am now on the lookout for one now.

Seriously nice work & seriously nice result. Well done.

Congratulations . It certainly went to a good home.

The Engine Rebuild and Upgrade story

I thought I’d write a piece about the engine.

I’ve already hinted and mentioned some upgrades, so here goes with the full list.

I sent the engine via courier to Jim Cray, on a crate, with the carbs in a box, a deep sump and the air cleaner and starter covers (for completeness for vapour basting) - see the photo. This was about 13 Feb 21. After arrival and inspection it became apparent that the crank had been split before to re-grind the big ends. The re-riveting of the counter-weights had not gone well and the front journal had been overheating. A new crank was required. Luckily, I had a spare so that was dispatched to Jim, who passed it sound for installation.


I bought a Dynatek ignition system with leads, coils and brackets through Jim.

The job list read:

Dellortos: new floats, float needles and gasket/seal sets. The carbs were stripped, overhauled and rebuilt.

Engine: new inlet and exhaust valves and guides, unleaded seats, a pair of rockers, all rocker bearings, support tubes, a replacement rocker cover (good used), all gaskets, timing chain kit, front crank bearing, pair of con-rods (good used), big end shells, big end bolts, main bearings, oil pump rotor and cover, pressure relief valve spring, post-81 sump pick-up (good used), crankshaft sprocket, cam bolts, flywheel bolts (I had already done a later flywheel conversion and gearbox mods to suit), oil pressure switch, clutch bolts/washers and last but not least, spark plugs.

Upgrades: The engine was fitted with a Siebenrock power kit (1000cc, nikasil bores with new pistons and rings) and the whole lot dynamically balanced. The heads were twin-plugged. He also lightly gas-flowed the ports. I asked Jim to get the barrels painted black to suit the R90S engine colour scheme.

Naturally, I was keen to fetch the engine after all this so I drove to Faversham on 25 May 21* and spent a few hours in the shop with Jim and Kris (fellow worker/experienced apprentice) and asking questions, mainly about ignition setting up and what to do with the first service. These engines are best transported in the boot with a pair of motorbike tyres stacked as a cradle for the engine to sit in. I got a couple of boxes full of the old parts from the engine.

The Dynatek uses the existing advance/retard weights but has hall sensors (one for each cylinder) which are adjustable so that you don’t get a blurred image with a strobe timing light. This also helps with engine vibrations. I was able to set the bike up statically and get good confirmation when dynamically testing.

*During lockdown and with Brexit, the supply of some of the new, original parts was difficult, delaying the build.

Update

I attended the Airhead day at Sammy Millers (see picture, 10 July 2022) but really to report I was unhappy with the handling of the bike after the rebuild. So what did I do to get it better? Firstly, the original rear shocks went and I tried a pair of second-hand Koni Dial-a-Rides. They massively improved things and are not leaking (yet) but they are rebuildable (checked with IKON UK) if they cause trouble. The front was next; I put a set of progressive springs in and voila, the bike is now very happy to be put through its paces! So one mustn't forget the basics when doing restorations - if it's worn out don't just polish it! The original front springs, one was at the bottom spec length and the other was about 6mm shorter. Very tired.

I had a leaky (well, it was pissing out) right carb which prevented an early start to Sammy Millers. I found the float was stiff on the pivot. So I removed the pivot pin and shaved a minute amount off the float pivot tube. That worked. As a precaution I did the other one today (my left boot was smelling of fuel!).

Other work has been to replace a leaky rear seal in the bevel drive (tell-tale oil from the hole next to the drain plug). My new brake pressure switch failed so I had to revert to a good spare. I traded both kidneys for a new (refurbished and zeroed) speedo from Germany. And I fitted a NAV6 cradle to help me get to Spain in September....

Shots taken by MC Indianos during the North of Spain Rally 2022

'Slow Rider' took these pictures whilst I was in Spain. What a great trip!

As the blog is still open I thought I'd do a quick update. After Spain last year I had a faff with the front brakes and set about sorting them out. I also thought that, good as the performance was, and average 55mpg on the trip to Spain was surprisingly good, there was something that could be done with the 'tuning'. My other twin-plugged bike is super-smooth and the R90S was smooth but not 'super'.

So I asked Jim Cray to try and work some magic. Although he had refurbished the engine, I had done the ignition and final tuning of the carbs. So, fast forward to getting it back, he sorted my front brakes (one caliper was 'way-out' apparently ), found I couldn't get WOT due to a worn twist-grip bevel so replaced with new, and changed the Dynatek for an Endurolast crank ignition system. And tuned it all.

All I can say is that it is a different bike. Super-smooth. Very quick. And stops. Starts and ticks over on the choke. Pulls from below 1500rpm. Just amazing.

So hats off to Jim Cray. He and his contemporaries won't be trading forever. So if you were thinking of getting your bike 'done' by a master, be quick about it!

I would imagine that those /7 series two tone 'fade' paint jobs are amongst the hardest for painters to reproduce. Yours looks absolutely perfect - great work.

The Other PaulG said:

I would imagine that those /7 series two tone 'fade' paint jobs are amongst the hardest for painters to reproduce. Yours looks absolutely perfect - great work.

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Great work indeed, but not mine - echoing my last comment about using 'masters' of the trade. Finding one who knows his stuff and was working at the time these bikes were new - I've been fortunate. There's a lot of corporate knowledge in these forums, right here!
And BTW those paint jobs are /6 ones.